Popular Additive Manufacturing Research Articles

Theoretical evolution of thermal behaviour of Ti-6Al-4V subjected to selective laser melting: A powder free approach

Additive manufacturing (AM) processes are considered to be the pillar of the next industrial revolution due to their inherent qualities such as design flexibility, the ability to produce complex parts and prototypes, lower cost due to the reduced requirement of materials and curtailed lead time for manufacturing. Selective laser melting (SLM) is one of the most popular metallic AM technologies since it enables accurate control over part dimensions and fabrication of high resolution features. This research paper is aimed to develop an exact analytical model of three-dimensional thermal response captured in SLM of Ti based alloy (Ti-6Al-4V). A physical model has been proposed to predict the temperature profile during the metal additive manufacturing process with consideration of the effect of thermal history developed during moving laser heat source interaction. The corresponding mathematical solution is developed by employing an amalgamation of ‘Duhamel’s theorem’ and ‘Finite Integral Transform method’. The parametric laser-substrate interaction phenomenon is the prime deciding factor for the successful accomplishment of the manufacturing process. This research paper theoretically investigates the thermal characteristics (peak temperature, temperature distribution curvature, pulse time, optical penetration depth, time of laser exposure, laser absorption radius, and so on) by employing Fourier’s heat conduction model with a moving laser heat source. The theoretical estimation has been validated by the existing mathematical as well as experimental research outcomes. Present work might be an asset for deciding the design of process variables and protocols in terms of laser based additive manufacturing specifically the selective laser melting process.

Effect of Raster Angle and Infill Pattern on the In-Plane and Edgewise Flexural Properties of Fused Filament Fabricated Acrylonitrile–Butadiene–Styrene

Fused Filament Fabrication (FFF) is a popular additive manufacturing process to produce printed polymer components, whereby their strength is highly dependent on the process parameters. The raster angle and infill pattern are two key process parameters and their effects on flexural properties need further research. Therefore, the present study aimed to print test specimens with varying raster angles and infill patterns to learn their influence on the in-plane and edgewise flexural properties of acrylonitrile–butadiene–styrene (ABS) material. The results revealed that the highest in-plane and edgewise flexural moduli were obtained when printing was performed at 0° raster angle. In comparison, the lowest values were obtained when the printing was executed with a 90° raster angle. Regarding the infill pattern, the tri-hexagon pattern showed the largest in-plane modulus, and the quarter-cubic pattern exhibited the greatest edgewise flexural modulus. However, considering both the modulus and load carrying capacity, the quarter-cubic pattern showed satisfactory performance in both planes. Furthermore, scanning electron microscopy was used to investigate the failure modes, i.e., raster rupture, delamination of successive layers and void formation. The failure occurred either due to one or a combination of these modes.

Effect of an Adaptive-Density Filling Structure on the Mechanical Properties of FDM Parts with a Variable Cross-Section.

Fused deposition modeling (FDM) technique is one of the most popular additive manufacturing techniques. Infill density is a critical factor influencing the mechanical properties of 3D-printed components using the FDM technique. For irregular components with variable cross-sections, to increase their overall mechanical properties while maintaining a lightweight, it is necessary to enhance the local infill density of the thin part while decreasing the infill density of the thick part. However, most current slicing software can only generate a uniform infill throughout one model to be printed and cannot adaptively create a filling structure with a varying infill density according to the dimensional variation of the cross-section. In the present study, to improve the mechanical properties of irregular components with variable cross-sections, an adaptive-density filling structure was proposed, in which Hilbert curve with the same order was used to fill each slice, i.e., the level of the Hilbert curves in each slice is the same, but the side length of the Hilbert curve decreases with the decreasing size of each slice; hence, the infill density of the smaller cross-section is greater than that of the larger cross-section. The ultimate bearing capacity of printed specimens with the adaptive-density filling structure was evaluated by quasi-static compression, three-point bending, and dynamic compression tests, and the printed specimens with uniform filling structure and the same overall infill density were tested for comparison. The results show that the maximum flexural load, the ultimate compression load, and the maximum impact resistance of the printed specimens with the adaptive-density filling structure were increased by 140%, 47%, and 82%, respectively, compared with their counterparts using the uniform filling structure.

Role of build orientation on quasi-static and dynamic fracture responses of additively manufactured AlF357 and AlSi10Mg alloys

In this work, a popular additive manufacturing (AM) aluminum alloy - AlSi10Mg and a new AM aluminum alloy - AlF357 are fabricated using Laser-Powder Bed Fusion ( L -PBF) approach to evaluate quasi-static and dynamic fracture behaviors. Four build orientations - horizontal, vertical, flat, and diagonal - are assessed. A Kolsky pressure bar apparatus along with ultrahigh speed photography is used to carry out the dynamic fracture experiments. In-plane surface displacements near cracks are measured using Digital Image Correlation (DIC) to evaluate the fracture parameters directly. A hybrid experimental-numerical approach that combines DIC measurements and finite element analysis is implemented to extract critical energy release rate and crack growth resistance behaviors. The effect of build orientation is found to be significant on the quasi-static fracture behavior with the horizontal and flat orientations having the best and worst fracture responses, respectively. Under dynamic loading conditions, however, the effects of build orientation are marginal. Both AlF357 and AlSi10Mg show strain-rate sensitivity and change in fracture mechanism under dynamic loading conditions with ~175% and ~200% increase in critical energy release rate. AlF357 consistently outperforms AlSi10Mg in both quasi-static (~30%) and dynamic (~10%) loading conditions.

Behaviour evaluation of 3D printed polylactic acid under compression

Additive manufacturing is one of the most promising production technologies introduced in the last years. One extensive field of application of additive manufacturing is for prototyping, but 3D printed parts have also the potential to meet the requirements for functional components or production support. Fused filament fabrication (FFF) is the most popular additive manufacturing processes because of flexibility, reduced costs, and number of available materials concerning thermoplastics. Some of these materials have good thermal, electrical and mechanical properties, however they also exhibit a high dependence on process parameters and, in general, have lower properties than if the material is processed and manufactured by a classic process. In this paper monotonic, fatigue and creep behaviour of PLA under compression is studied, using cylindrical specimens tested according to ASTM D695, ISO 527, ASTM D7791 and ASTM D2990. A Design of Experiments was conducted to identify and quantify the effects of printing parameters on the compression behavior of these specimens. From best set of parameters, specimens were fabricated and tested under tension, fatigue (compression–compression) and creep (compression) to identify their performance and the failure mechanisms. It was observed that compressive strength is linearly dependent with the density of the samples, but for fatigue no such relation was found. The results obtained characterize the behaviour of PLA material produced by FFF under compression and can be useful for quality control and to support the design of parts that to work under compressive loads.

An orientation-field based algorithm for free-form material extrusion

Material extrusion is a popular additive manufacturing process that gained prominence in various industrial applications. The current work addresses the limitations of the existing slicing software in producing parts with customized filament layouts. A new filament deposition algorithm that produces filament paths taking as input arbitrary point-wise orientation fields is presented. Like slicing software, it can control various process parameters, including extrusion width, layer height, filament spacing, number of layers, printing and travel speeds, and produces G-Code instructions. Capabilities of the algorithm are presented by producing parts with both partial and maximum infill and parts with a multi-oriented layer stacking sequence. The results show that the algorithm can print parts with filaments oriented along the input orientation field at different infills, thus making this contribution a potential tool for many applications that demand customized filament placement. • A new 3D printing algorithm to extrude filaments along a given orientation field. • The algorithm controls all crucial 3D printing parameters like a slicing software. • Readily 3D-printable G-code instructions are produced as output. • The algorithm can be employed for 3D printing optimized anisotropic structures.

Development of Carbon Nanotube‐Reinforced Nickel‐Based Nanocomposites Using Laser Powder Bed Fusion

Modern aerospace applications demand the development of high‐performance components with advanced materials. The development of nanomaterial‐reinforced metal matrix composites is a practical approach to improve properties. Laser powder bed fusion (LPBF) is one of the popular additive manufacturing approaches to fabricating metal parts with complex geometric structures. This research investigates multiwalled carbon nanotube (CNT)‐reinforced nickel‐based alloy (Haynes 230) nanocomposite for property improvement. Three volumetric concentrations (0%, 2.5%, and 5%) of CNTs in the metal matrix are investigated with different printing parameters. Different characterizations are conducted on the test specimens. Results show that LPBF‐printed Haynes 230 with 2.5 vol% CNTs has higher relative density (99.36%) and less porosity compared to those printed with 5 vol% CNTs. Mechanical test results show that LPBF‐printed Haynes 230 with 2.5 vol% CNTs has the highest hardness, modulus of elasticity, yield strength, and ultimate strength than those printed with as‐received Haynes 230 powder (with 0 vol% CNTs), Haynes 230 with 5 vol% CNTs, and commercial Haynes 230 plates. The strengthening behavior of the CNTs in the metal matrix composites is discussed in this paper. The potential of CNT‐reinforced nickel‐based nanocomposites for applications requiring materials with outstanding mechanical properties, such as aerospace and defense, is demonstrated.

Effect of the manufacturing parameters on the tensile and fracture properties of FDM 3D-printed PLA specimens

Fused Deposition Modeling (FDM), also known as material extrusion, is currently one of the most popular Additive Manufacturing (AM) technology on the market. In this study, two commercial FDM printers (Prusa i3 MK3 and WN400 3D Platform) were used for layer-by-layer manufacturing of polylactic acid (PLA) Dog Bone (DB) and Single Edge Notched Bend (SENB) specimens, aimed at investigating the influence of the manufacturing parameters on the tensile and fracture properties of PLA elements obtained by FDM technology. The effects of growing direction (horizontal and vertical), building orientation (0°, 45° and 90°), printer type, layer thickness (0.15 and 0.40 mm), specimen thickness (4 and 10 mm) and filament color (purple, white, black, gray, red, orange) are discussed in detail. Tensile tests were performed on DB specimens, while fracture mechanics tests on SENB specimens. Both the tensile and fracture properties of FDM 3D-printed PLA specimens have been found to be dependent on the investigated manufacturing parameters. From the microstructural analyses of the SENB fracture surfaces, it has been observed that the fracture mechanisms and crack propagation is a step-wise process. Finally, the material properties charts (Young’s modulus and mode I fracture toughness versus tensile strength) are plotted.

Electric field assisted fused deposition modeling for improving nozzle cleanliness

Fused deposition modeling (FDM) is one of the most popular additive manufacturing processes. It has been utilized in a variety of research fields and applications. However, little attention has been paid to the nozzle cleanliness issue in the FDM process. Debris of extruded polymer materials can easily build up on the nozzle surface in the printing process and the accumulated debris typically falls on the actual printing area, which degrades the quality of printed parts. This paper innovated an approach to reduce polymer debris build-up on the nozzle during the FDM printing process. An electric-field-assisted FDM (E-FDM) process was proposed to improve the nozzle cleanliness. E-FDM utilizes a high voltage power supply to generate an electrostatic force between the nozzle and build plate, which has great potential to avoid accumulations of melted thermoplastic materials on FDM nozzles. To verify the effectiveness of the E-FDM process, both E-FDM and conventional FDM processes were used to print test specimens for certain durations of time. Debris built up on the nozzle surface was characterized by 3D scanning to quantify the volume changes of the nozzle. The E-FDM printing reduced debris accumulation by 47% after ∼5 hours of printing and over 80% after ∼15 hours of printing as compared to the conventional FDM process. The results demonstrated the effectiveness of the electric-field-assisted FDM process in reducing the nozzle debris built up on the nozzle surface.

An approach to improve the microstructure and mechanical properties: A hybrid manufacturing of laser directed energy deposition and shot peening

As one of the most popular additive manufacturing technologies, laser directed energy deposition (LDED) has been extensively and deeply studied to improve the microstructure and properties of formed materials. Hybrid additive manufacturing(HAM) of LDED and shot peening is an innovative technology that combines the principle of surface strengthening and additive manufacturing. It can improve the mechanical properties and optimize the microstructure of the formed materials by strengthening the surface layer-by-layer. In this paper, the phase, oxygen content, microstructure, tensile properties, hardness and fracture morphology of the samples formed by LDED and HAM are compared. It is found that the mechanical properties of the forming samples are significantly improved by HAM, and the yield strength, ultimate tensile strength and average hardness are increased by 53%, 12% and 7%, respectively. Meanwhile, the microstructure of the sample is improved, some of the coarse columnar grains are refined, the heterogeneity of grain size is reduced, and the fibrous microstructure between layers is reduced. The hybrid additive manufacturing of LDED and shot peening can achieve high efficiency and high quality integrated manufacturing of forming parts, which is expected to promote its efficiency and applicability in practical cases in the future.

Characterization and parametric optimization of additive manufacturing process for enhancing mechanical properties

Additive manufacturing (AM), also known as 3D printing, is a cutting-edge industrial production technique that enables the creation of lighter, stronger components and systems. Fused deposition modeling (FDM) is a popular AM process for creating prototypes and functional components out of common engineering polymers. The mechanical characteristics of printed items are dramatically altered as a result of various process factors. As a result, it is critical to examine the impact of printing settings on the quality of the printed item. In terms of flexural strength, this study presents an experimental examination into the quality analysis of parameters on printed components utilizing FDM. By adjusting process factors such as layer height, raster width, raster angle, and orientation angle, the experiment was carried out utilizing Taguchi's L18 mixed orthogonal array approach. The UNITEK-94100 universal testing equipment was used to evaluate the flexural strength of Acrylonitrile butadiene styrene (ABS) specimens that had been conditioned as per ASTM D790 standard. The impacts of parameters on experimental results were examined and optimized using the hybrid genetic algorithm with response surface methods, response surface approach, and Taguchi method. When the optimal solutions of each technique were studied, the response surface approach and Taguchi methods were determined to be less promising than the genetic algorithm method.

Optimization of Printing Parameters to Maximize the Mechanical Properties of 3D-Printed PETG-Based Parts.

Fused filament fabrication (FFF) is the most popular additive manufacturing method, which allows the production of highly complex three-dimensional parts with minimal material waste. On the other hand, polyethylene terephthalate glycol (PETG) has been used to replace traditional polymers for 3D printing due to its chemical resistance and mechanical performance, among other benefits. However, when fibres are added, these PETG-based composites can be suitable for many different applications. Nevertheless, to guarantee their good performance in-service in these applications, and even extend to new ones, it is necessary for their mechanical properties to be maximized. Therefore, this study intends to optimize the printing parameters (nozzle temperature, printing speed, layer height and filling) in order to maximize the mechanical properties of printed PETG, PETG+CF (carbon fibre-reinforced PETG composites) and PETG+KF (aramid fibre-reinforced PETG composites). The Taguchi method was used for the experimental procedure design, and the specimens were produced according to the L16 orthogonal array. Finally, an analysis of variance (ANOVA) was performed, with a 95% confidence interval, to analyse the effect of the printing parameters on the bending properties. It was possible to conclude that the best bending properties for PETG, PETG+CF and PETG+KF were obtained for extrusion temperatures of 265 °C, 195 °C and 265 °C, printing speeds of 20, 60 and 20 mm/s, layer heights of 0.4, 0.53 and 0.35 mm and an infill density of 100% for the three materials, respectively.

Machine Learning-Based Void Percentage Analysis of Components Fabricated with the Low-Cost Metal Material Extrusion Process.

Additive manufacturing (AM) is a widely used layer-by-layer manufacturing process. Material extrusion (ME) is one of the most popular AM techniques. Lately, low-cost metal material extrusion (LCMME) technology is developed to perform metal ME to produce metallic parts with the ME technology. This technique is used to fabricate metallic parts after sintering the metal infused additively manufactured parts. Both AM and sintering process parameters will affect the quality of the final parts. It is evident that the sintered parts do not have the same mechanical properties as the pure metal parts fabricated by the traditional manufacturing processes. In this research, several machine learning algorithms are used to predict the size of the internal voids of the final parts based on the collected data. Additionally, the results show that the neural network (NN) is more accurate than the support vector regression (SVR) on prediction.

Non-Destructive and Destructive Testing to Analyse the Effects of Processing Parameters on the Tensile and Flexural Properties of FFF-Printed Graphene-Enhanced PLA

The significance of non-destructive testing (NDT) methods cannot be overstated as they help to evaluate the properties of a material without damaging/fracturing it. However, their applicability is dependent on their ability to provide reliable correlation with destructive tests such as tensile and flexural. This correlation becomes more problematic when the material is not homogeneous, such is the case with parts manufactured using a popular additive manufacturing process termed as fused filament fabrication (FFF). This process also requires optimisation of its parameters to achieve desired results. Therefore, this study aims to investigate the effects of four different nozzle temperatures, print bed temperatures, and print speeds on FFF-printed Haydale’s Synergy Graphene Enhanced Super Tough PLA through three non-destructive (ultrasonic, hardness, strain) and two destructive (tensile, flexural) testing methods. Samples were manufactured using Anet® ET4 Pro 3D printer and evaluated as per British and International standards. Two non-destructive tests, i.e., ultrasonic and hardness have been associated with evaluating the tensile properties of the manufactured parts. These results were correlated with destructive tensile testing and showed good agreement. The NDT method of strain measurement showed a very good correlation with the destructive three-point flexural test and was able to provide a reliable evaluation of flexural properties as a function of all three processing parameters. The results presented in this work highlight the importance of NDT methods and how they can be used to evaluate different properties of a material.

Design and testing of a digital twin for monitoring and quality assessment of material extrusion process

In this paper are illustrated conception, realization and validation of an original solution for the digital twin of a material extrusion 3D printer, the most popular additive manufacturing machine. The system is composed by three main modules: a core containing the simulation engine, a data interface managing incoming data and a graphical interface enabling user remote control. It receives as input the process data collected by several sensors and the same part program (G-Code file) used by the real machine; thus, the system provides various real time functions for process monitoring, condition monitoring and geometrical accuracy control. Alongside detecting load on critical components and checking wear and tear, it can also systematically sort data collected or calculated during operation to help in optimizing printing parameters. Through interaction with the print host software, the twin is able to intervene directly in the current process to pause printing in case of anomalies and to assist users along a recovery procedure. An index of quality of the printed piece is obtained by comparing the CAD model of the printed part and a 3D model of the deposited material powered by the data coming from the machine. The system has been tested on a custom-made Cartesian printer: a number of prints were made with different speeds and accelerations to assess the impact of these settings on the average quality, and a more in-depth study was carried out on the digital models of the prints to investigate the origin of the defects detected. The programs and devices used do not rely on commercial solutions, so that the system is easily replicable.

Mechanical characterisation of AM nylon-matrix carbon-fibre-reinforced composite in tension

The ability of additive manufacturing (AM) to produce structures with complex geometry has gained significant attention from researchers and fused deposition modelling remains a popular AM method to fabricate a layered structure using thermoplastic polymer. However, the application of these materials remains limited to prototyping because of weak performance associated with manufacturing defects; porosity and weak interfaces. Stronger composite structures may be produced through optimisation of processing parameters and addition of reinforcing fibres in the polymer to expand the application of products, e.g., in medical prosthetics and protective gear. This study investigates the fracture behaviour of AM nylon matrix composites reinforced with short and continuous carbon fibres under tensile load. Additionally, the impact of fibre volume fraction on mechanical properties of the composites is explored through comparison with literature. Tensile testing on unidirectional solid specimens loaded in the fibre direction revealed that nylon reinforced with 5% of continuous carbon fibre had significantly higher tensile strength and Young’s modulus but lower elongation at break compared to nylon reinforced with 20% short carbon fibre thanks to the superior performance of continuous fibres. Post-experimental fracture surfaces of both materials revealed brittle failure with fibre pull-outs for the composite with continuous fibres, indicating weak bonding between the nylon matrix and the carbon fibre. The mechanical properties (stiffness and tensile strength) of both materials for different levels of fibre volume fractions are presented based on this study and literature data. The tensile strengths and moduli changed in a similar manner for both materials, but an almost linear relation was obtained for nylon reinforced with continuous carbon fibre at higher fibre content as the properties of the composite structures were governed mostly by fibres. On the contrary, for the composite reinforced with short fibres at lower fibre content, no direct relationship was observed.

Annealing effect on mechanical properties of 3D printed composites

Fused filament fabrication (FFF) is the most popular additive manufacturing method, with which it is possible to obtain highly complex three-dimensional parts without wasting materials. In order to improve the mechanical properties of 3D printed materials, literature suggests the thermal annealing process. Therefore, this work aims to study the effect of thermal annealing on the bending properties of PETG and PETG reinforced with carbon and aramid fibres. For this purpose, the samples were printed using a B2X300 printer, with a hardened steel nozzle of 0.6 mm diameter, and the printing parameters were optimized for each material. Five specimens were tested according to ASTM D790-17 for each condition. Three temperatures (90ºC, 110ºC and 130ºC) and three annealing times (30 min, 240 min and 480 min) were used to study the benefits obtained with the thermal annealing. Finally, the samples were evaluated in terms of geometrical parameters, hardness, and flexural properties. Regardless of the materials studied, the best mechanical properties were obtained for the highest temperature and the longest exposure time, but due to the high geometric distortions, a temperature of 90 °C and an exposure of 30 minutes proved to be more effective.

The recent development of vat photopolymerization: A review

Vat photopolymerization (VPP) is one of the most popular additive manufacturing technologies. It has gained significant attention among academia as well as industry due to its high speed, high accuracy, and broad applications in areas such as functional devices, ceramics, and biomedical etc. However, due to the rapid proliferation of this technology, there is a lack of a comprehensive review in these aspects (i.e., its printing speed, resolution, multi-material capability, and new applications). In this review paper, the recent developments of VPP technologies are reviewed, including ultrafast VPP, high resolution VPP, and multi-material VPP. The emerging applications of VPP are discussed with a focus on the booming application in biomedical area. Finally, the current challenges and a perspective on the future directions of VPP are provided.

Analyzing the Impact of Print Parameters on Dimensional Variation of ABS specimens printed using Fused Deposition Modelling (FDM)

Fused Deposition Modelling is the most popular additive manufacturing technique. Its ability to build complex designs in limited time and money makes it more accessible than other AM techniques. Many Industries employ this technique in Prototyping, tooling, and mold design. However, the dimensional accuracy of the printed part is susceptible to deviations with changes in print settings, this drawback of FDM affects its employability in large scale manufacturing, where repeatability is of paramount importance. Therefore, in this paper the impact of six significant print parameters; wall thickness, infill density, build plate temperature, print speed, layer thickness and extrusion temperature on the dimensional accuracy of the printed specimens have been studied. The material chosen for the study is Acrylonitrile Butadiene Styrene (ABS). The experiments were conducted using a small resolution central composite design (CCD) and it was found that layer thickness and print speed have the most significant impact on the dimensional accuracy of the printed parts, it is also observed that lower values of layer thickness and higher print speed result in better dimensional accuracy.

Characterization of continuous carbon fibre reinforced 3D printed polymer composites with varying fibre volume fractions

Fused deposition modelling (FDM) is one of the most popular additive manufacturing (AM) technique which is used to investigate the elastic properties of 3D printed polyamide-based polymer composites structures. The aim of this work is to study the mechanical properties of continuous carbon fibre reinforced polyamide polymer composite samples using tensile and flexural testing by varying the fibre volume contents with applying pressure, temperature and holding the samples for 60 minutes in the platen press. The results showed that the strength and stiffness increased with the increase in fibre volume content (fraction). Hot pressed samples exhibited the increase in tensile strength by about 27 % and elastic modulus by 11 % because of increasing the fibre volume fraction from 29 % to 35%. Synergetic effect of both short and continuous carbon fibre was also studied, and it was observed that the tensile properties were higher for the samples reinforced with short and continuous fibre than only continuous fibre polymer composites. Effects of voids on 3D printed continuous carbon fibre-reinforced polymer composites were quantified. A microstructure study of the 3D printed polymer composites was carried out using scanning electron microscope (SEM). Following SEM analysis on the tested specimens, it was observed that there was a strong correlation between the mechanical properties and the microstructure. Fibre volume fraction was measured using acid digestion method to determine the amount of fibre contents before and after hot pressing (compaction). From Micro- Computed Tomography (µCT) it was confirmed that hot pressing reduced the void content which in return increased the strength and modulus.